Generally in the prior art it has been known to use mineral fillers to modify the properties of flexible thermoplastic resins. These thermoplastics resins were filled at low levels because it would be expected that high levels of fillers would adversely affect the physical properties of the resins. It has been found that with fillers selected from the group consisting zinc oxide, barium sulfate, zirconium oxide, zirconium silicate or mixtures thereof, it is possible to incorporate, up to 90% by total weight of composition, of filler. These filled flexible thermoplastics are opaque to x-rays and may be molded or thermoformed into x-ray barriers for use in protecting radiation sensitive materials such as photographic film. These materials may also be formed into structural elements, that may be used to protect medical and industrial personnel from exposure to direct x-radiation or reflected x-rays.
The flexible thermoplastic resins within the scope of the invention include those which when filled with from 20-90% by total weight of composition of barium sulfate, zinc oxide, zirconlure oxide, zirconium silicate or mixtures thereof, are substantially free of internal voids and will have a flexural strength of less than 7500 psi when tested according to ASTM D-790.
Accordingly, it is a primary object of the invention to provide novel thermoplastic molding compositions which include high levels of fillers and are flexible.
It is also an object of this invention to provide novel thermoplastic molding compositions which have good surface properties and may be molded into complex shapes.
It is also an object of this invention to provide novel thermoplastic molding compositions which have a density greater than 1.0.
These and other objects of the invention will become apparent from a review of the present specification.